1. Field of the Invention
The present invention relates to metallurgical recycling of engineering industry waste products, preferably chips, in particular, titanium alloys chips. The product of processing in the form of consumable electrodes can be used for secondary titanium alloys manufacture, as well as in ferrous metallurgy for steel alloying.
2. Description of Related Art
The most commonly known, (about 45% of the total amount of factory metallic waste products), and the most difficult to be recycled, sort of waste products is chip scrap. The difficulty of preparation of which for recycling consists in it's great volume, contamination with emulsion, machining oil contamination, as well as contamination with foreign particles of another metals and hard alloys. At present time only a minor amount of chip scrap waste products is recycled, the greater part of it presenting an environmental burden without deriving economic benefits.
One current method for producing consumable electrodes using 10-15% of chip scrap, and the rest is—titanium sponge (Kiparisov S. S. and others. Titanium scrap processing, M., 1984, issue 1.), is characterized in that, at first briquettes are pressed, further said briquettes are welded in argon into consumable electrode. A limitation of said method is the use of a considerable amount of expensive titanium sponge, and insufficient mechanical strength of the electrodes, which can lead to destruction thereof during refining.
Another method for obtaining consumable electrodes (Filin Yu. A. and others. Processing and use of titanium waste products in foundries, jorn. “Liteinoe proizvodstvo”, 2000, No. 7, p.21.) from foundry titanium bulk scrap and briquetted chip scrap is characterized by packing bulk scrap and chip scrap briquettes into a mould with further filling up the mould with liquid alloy of the same name, which fills interstice between the scraps and briquettes and forms a consumable electrode. The main limitation of this method is the small portion of chip scrap waste products used, since considerable party by weight of (furnace) charge is filled up with bulk scrap, alloy and titanium sponge.
Another method for producing consumable electrodes (Abramova K. B. and others. Briquetting of titanium chip scrap under the influence of electric current sharp pulses, jorn. “Tsvetnye metally”, 1998, No. 12, p. 70-74.) is characterized by like alloy titanium bulk scrap and chip scrap briquettes placed into a mould (the share of chip scrap in a (furnace) charge is 5-10%). The limitations of this method are as follows: low rate of chip scrap waste products used, and considerable oxygen content in the ingot obtained after remelting the electrode manufactured in accordance with said method, since owing to chip scrap contamination in case of one percent increase of number of briquettes in (furnace) charge results in oxygen content rise in secondary alloy by 0.008%.
Another method for producing consumable electrodes from titanium and alloys thereof (Patent RF No. 2081727, B22 27/00, 1997, No. 17), uses scrap, clipping and chip scrap. The method is characterized in that preliminarily preparation of (furnace) charge, its placing into a mould and filling up with molten alloy is carried out. When a (furnace) charge is used in form of chip scrap briquettes, said chip scrap briquettes are loaded into the mould with clearance, which provide mould volume infill with molten metal; and before filling up the mould is heated up to 300-350 deg C. Furthermore, depending on charging volume of the mould with (furnace) charge different methods for filling in molten metal are used. Said method has the same limitations as the previously cited methods, namely, low rate of chip scrap waste products used in metallurgical recycling and considerable interstitial impurities content such as carbon, oxygen, hydrogen and nitrogen which lead to mechanical degradation of secondary alloys, obtained after remelting the electrodes. Moreover, deficient heating of the mould before infill can result in crumbling of chip scrap during electrode refining because of weak diffusion adhesion of briquettes' material and molten alloy.